Cytometry is a technical specialty concerned with the counting and characterization of biological cells. FIG. 1 shows a simplified diagram of a system for performing a technique known as imaging flow cytometry. In a basic form of imaging flow cytometry, cells 101 are suspended in a fluid and entrained single-file in a narrow transparent tube 102. The entrainment can be accomplished by any of several methods, including hydrodynamic focusing. A light source 103 illuminates each cell 101 as it passes a measurement location. Light source 103 may be, for example, a laser. Light from light source 103 is scattered by the cell 101 being measured. Some light 105 is gathered by an objective lens 106 and redirected to form an image at a light sensor 107. Light sensor 107 may be, for example, a component of a microscope or camera. Various optical components may cooperate with objective lens 106 in directing light 105 to sensor 107, including, for example, partially reflective mirror 108 and an additional lens 109. Output signals from sensor 107 are sent to a processing unit 110, which may store and analyze the signals to discern information about each cell, for example its size and some information about its internal structure.